1. Field of the Invention
The present invention relates generally to medical cannulas and stylets used to obtain soft tissue biopsy specimens, and more specifically, to an apparatus and method for acquiring multiple biopsy specimens from a selected target tissue while requiring only a single cannula placement in a manner which may be confirmed using CT scanning or other imaging techniques.
2. Description of the Prior Art
Biopsy of abnormal tissues in animals and humans for diagnosis is a common procedure. Many forms of biopsy apparatus are known; typically, such apparatus includes an outer cannula having a distal end and adapted to slidingly receive a stylet or needle. The biopsy needle or stylet typically occludes the distal end of the cannula to prevent tissue coring as the cannula is advanced into the patient. The stylet or biopsy needle also typically includes a specimen retaining notch which is covered by the outer cannula as the cannula is advanced into the patient toward the target organ or target tissue mass. Once the outer cannula is positioned in the target organ or tissue mass, the distal end of the stylet is advanced relative to the distal end of the cannula for exposing the specimen retaining notch and allowing tissue proximate thereto to prolapse within the specimen retaining notch. Thereafter, the distal end of the outer cannula is further advanced to slide over the specimen retaining notch to simultaneously cut the tissue prolapsed within the specimen retaining notch and to retain such specimen therein. The specimen may then be removed for analysis, either by simultaneously withdrawing both the outer cannula and inner biopsy needle, or by withdrawing only the biopsy needle while leaving the outer cannula in place. The latter option is preferred in those instances when either multiple specimens, or specimens taken from multiple depths, are required or preferred.
In Gazelle et al., "Guided Percutaneous Biopsy of Intra abdominal Lesions", AJR 153: 929-935, November 1989, the authors describe methods for performing multiple pass biopsies; one such method is the double-needle (short cannula coaxial) method wherein a larger-caliber short needle is placed through the skin to serve as a guidance cannula; once its direction is confirmed, a small needle is moved coaxially through the larger needle to the lesion. Multiple passes are performed by leaving the guidance cannula in place and repeating the insertion of the smaller needle.
While manually-operated biopsy devices for cutting tissue specimens are known, they are often difficult to manipulate, particularly since the physician or technician must manipulate the cannula and the inner stylet or needle in proper timed sequence to reliably capture a tissue specimen. Moreover, it is preferred that the distal tip of the cannula be rapidly advanced over the specimen retaining notch, both to avoid dislodging the tissue prolapsed within the specimen retaining notch, and to avoid crushing the tissue specimen disposed therein.
In an effort to automate and/or mechanize the above-described biopsy procedure. Spring-loaded biopsy systems have been developed and made available for automating the timed sequence of manipulating the outer cannula and biopsy needle to obtain a tissue specimen. For example, Boston Scientific Corporation of Watertown, Mass. has made commercially available a mechanized biopsy system under the trademark "MEDITECH ASAP BIOPSY SYSTEM" wherein a stylet and surrounding cannula extend from a plastic handle. Thumb tabs are provided for the user to retract both the stylet and the surrounding cannula, whereby the specimen retaining notch of the stylet is covered by the cannula. After inserting the distal tip of the instrument at the edge of the region to be sampled, a trigger disposed on the handle unit is activated to sequentially advance first the stylet to automatically expose the specimen retaining notch and thereafter slide the distal end of the outer cannula thereover to sever and retain the tissue specimen.
Similarly, a one-handed, single-use, soft tissue biopsy cutting device is commercially available from The Perry Group, Ltd. of St. Louis, Mo. under the trademark "KLEAR KUT".
Within U.S. Pat. No. 4,699,154 issued to Lindgren, a tissue sampling device is disclosed for obtaining biopsy specimens wherein propelling springs are provided to sequentially advance an inner needle and an outer needle for capturing a tissue sample. A release button or trigger is provided upon the spring housing for triggering the timed sequence of the inner and outer needles.
A device substantially similar to that disclosed in the above-noted patent to Lindgren is commercially available from the Bard Urological Division of C.R. Bard, Inc. of Covington, Ga., under the registered trademark "BIOPTY". While sold to perform a biopsy of the prostate, the "BIOPTY" gun and related "BIOPTY-CUT" needle have also been proposed for performing CT-guided abdominal biopsies. See Parker et al., "Technical Note: Adaptation of the Bard Prostate Biopsy Gun for CT-Guided Abdominal Biopsies", CardioVascular and Interventional Radiology, (1989) 12: 50-52; and Parker et al., "Image-directed Percutaneous Biopsies with a Biopsy Gun", Radiology, June 1989; 171: 663-669. The BIOPTY-CUT 18-gauge needle is not adapted to be used apart from the BIOPTY gun, but needle placement is more cumbersome when the gun is attached. Parker et al. describe a technique of placing the BIOPTY-CUT needle within the body before attachment of the needle to the gun. A short section of sterile plastic sheath is inserted around the cutting needle between the hub of the cannula and the hub of the cutting needle to maintain the two in fixed relationship; following placement of the BIOPTY-CUT needle, the needle is "pinned" to the skin before the gun is attached to avoid displacement of the needle tip longitudinally or introduction of unwanted angulation. The short section of plastic sheath is removed, and the needle hub assembly is then inserted into the spring-loaded sleds of the BIOPTY biopsy gun.
However, the "MEDI-TECH" biopsy system, "KLEAR KUT", biopsy system, the tissue sampling device disclosed by Lindgren, and the BIOPTY biopsy system are all single-use devices, i.e., the outer cannula and inner stylet or needle are both removed as a unit after a specimen is obtained. To remove the tissue specimen trapped within the specimen retaining notch, the entire device, including the outer cannula, is withdrawn from the patient. However, the pathologist who must analyze such tissue specimens often prefers that multiple specimens be obtained, for example, at varying depths along the insertion tract. In such instances, the aforementioned mechanized biopsy systems must be repeatedly inserted and withdrawn to acquire such multiple specimens.
In U.S. Pat. No. 4,735,215, issued to Goto et al., a related mechanized biopsy instrument is disclosed. The biopsy instrument disclosed by Goto et al. differs in at least two respects from the mechanized biopsy instruments described above. First, the stylet of the instrument is not advanced by a spring-loaded mechanism; rather, the housing assembly of the device disclosed by Goto et al. includes a mechanism for retracting and subsequently advancing the outer cannula to first expose and then cover the specimen notch provided within the stylet. Secondly, the housing manipulated by the user is broken into two releasable halves, allowing the stylet to be withdrawn from the cannula without removing the cannula from the patient to facilitate the taking of multiple specimens.
However, all of the mechanized devices and instruments described above tend to be bulky and heavy. When the target tissue lies deep within patient, some form of imaging is commonly employed to direct the distal end of the biopsy system to the desired target. Such imaging techniques may include fluoroscopic, ultrasound, CT scanning, or MRI equipment. If fluoroscopy is used, the large handle associated with mechanized biopsy guns may obscure visualization of the target and needle tip. When performing a CT guided biopsy procedure, the physician must check the progress of the biopsy instrument intermittently while it is advanced toward the target. Such CT guided procedures require the physician to release his or her grip on the biopsy instrument to allow the patient to be transported through the scanner for imaging. However, the bulk of the mechanized biopsy instruments described above does not allow scanning to occur because the patient and the biopsy instrument cannot both fit into the scanning aperture Moreover, the weight of the handle housing for such devices is significantly great to deflect the outer cannula during scanning; therefore, the image that is obtained may not be an accurate indication of the direction of passage. The metal housing associated with some biopsy guns may degrade the CT scanned image by causing major artifacts, thereby limiting the physician's ability to see the position of the needle in the patient.
Even with respect to the aforementioned BIOPTY-CUT needle placement method described by Parker et al. for use with the BIOPTY biopsy gun, the authors state that the length of the BIOPTY-CUT needle poses gantry clearance problems during CT scanning, and they further state that the act of attaching the gun to the needle after localization can be awkward. Moreover, as already noted, Parker et al. state that the BIOPTY-CUT needle must be "pinned" to the skin before reattachment to the gun.
Accordingly, it is an object of the present invention to provide an apparatus and a method for acquiring biopsy specimens wherein the outer cannula and inner biopsy needle may be easily manipulated in timed sequence using an automatic, mechanized instrument or actuator.
It is another object of the present invention to provide such an apparatus and method wherein the proper placement of the outer cannula relative to the target tissue may easily be verified using CT guided scanning techniques or other imaging modalities.
It is still another object of the present invention to provide such an apparatus and method wherein multiple tissue specimens and/or tissue specimens from multiple depths along the same insertion tract, may be acquired without requiring the withdrawal of the outer cannula between successive specimens.
These and other objects of the present invention will become more apparent to those skilled in the art as the description thereof proceeds.